Abstract: Compositions and methods of non-invasive diagnosis are provided. The imaging agents include a linking groups and a reactive entity capable of reaction with a reactive functionality to form a covalent bond therewith. The imaging agents may be in the form of a bifunctional anchor molecule. The bifunctional anchor molecules have a functional group capable of activation which, when activated, may form a covalent bond with a reactive functionality on a target protein present in the mammalian vascular system, thereby “anchoring” the molecule to that target protein. The bifunctional anchors are also conjugated, either directly or indirectly, to a diagnostic agent of interest which provides the ability to diagnostically and non-invasively image the mammalian vascular space. Vascular targets include both cellular- and noncellular-associated proteins present in the mammalian vascular system.